This invention relates to a backup system and a storage system, and more particularly, to a backup system and a storage system using a log.
Data backup systems employing two computer systems are widely used. The data backup in this context implies a process of generating the same data as data contained in one computer system, and saving the generated data to the other computer system. The source computer system of the backup is referred to as an active system, and the destination computer system of the backup is referred to as a standby system. Moreover, data to be saved to the standby system is referred to as backup data. CHRISTOS A. POLYZOIS, HECTOR GARCIA-MOLINA, “Evaluation of Remote Backup Algorithms for Transaction-Processing Systems”, ACM Transactions on Database Systems, Vol. 19, No. 3, September 1994, Pages 423-449, for example, describes backup of data carried out by a duplex system.
Methods for the backup on the duplex system include a log transfer method. The log transfer method involves transferring a data update record (log) of the active system to the standby system, and generating backup data on the standby system. In the log transfer method, the backup data on the standby system is made coincident with the data on the active system when the backup starts. After the backup starts, a data update record of the active system is transferred to the standby system. The standby system updates the backup data based on the transferred data update record, thereby generating latest backup data. The log transfer method is described in CHRISTOS A. POLYZOIS, HECTOR GARCIA-MOLINA, “Evaluation of Remote Backup Algorithms for Transaction-Processing Systems”, ACM Transactions on Database Systems, Vol. 19, No. 3, September 1994, Pages 423-449.
Generally, a computer system includes an external storage system. The external storage system is a device which stores data on the computer system, and includes a hard disk or a disk array, which are magnetic storage systems.
Some external storage systems have a function of copying data between two systems. For example, an external storage system SANRISE9980V available from Hitachi Ltd. has a Hitachi True Copy function. The Hitachi True Copy function is a function of copying data on one SANRISE9980V to another SANRISE9980V by migrating the data over a network. When data is added to the external storage system of the source of copy, the same data is added to the external storage system of the destination of copy. Moreover, when data is overwritten on the external storage system of the source of copy, corresponding data is overwritten on the external storage system of the destination of copy.
The backup based on the log transfer method is carried out by a copy function of the external storage system. A description will now be given of a mechanism thereof. When the backup starts, the backup data on the standby system is made coincident with the data on the active system. A setting is made for copying a data update record between the external storage system of the active system and the external storage system of the standby system. When a data update record is added to the external storage system of the active system, the same data update record is added to the external storage system of the standby system. On the standby system, a server device updates the backup data based on a copied data update record, thereby generating the latest backup data.
A technology of notifying the server device of commands such as those for turning on/off a power supply is disclosed in JP 2007-310791 A. By employing the technology disclosed in JP 2007-310791 A, it is possible to carry out operations such as those for turning on/off the power supply for the server device via a network.
In general, an operation electric energy consumed by the server device when the power supply is turned on is larger than a standby electric energy consumed by the server device when the power supply is turned off. Accordingly, by properly controlling the power supply for the server device, it is possible to largely reduce the power consumption of the computer system.